Resin-based composite and restorative materials generally have very high cohesive strength, and accordingly are widely used in dentistry. Cements are used in dental materials as lining cements, luting cements, or for affixing orthodontic devices. Resin-based cements are utilized primarily for bonding of appliances such as veneers, inlays, onlays, crowns, and bridges. Resin cements generally provide excellent physical properties such as high compressive and tensile strength and low solubility, and are often used for bonding in difficult indirect bonding situations such as non-parallel or short crown preps. Generally, these cements are used in conjunction with dentin bonding agents to assure retention of the prosthodontic device. Another important class of curable dental materials is water-based resin-modified ionically hardenable cement. Cements of this category typically do not require additional adhesive. These cements have excellent biocompatibility, prevent or minimize post operative sensitivity, and are easy to clean up. Some of these cements, particularly the glass ionomer cements, also provide long-term fluoride release associated with cariostatic behavior.
Restorative filling materials are closely related to the cements mentioned above in chemical composition. In contrast to cements, however, restorative filling materials are more highly filled to provide higher viscosity, mechanical properties, and wear resistance. The setting characteristics should allow sufficient time for mixing the material to the restoration or tooth preparation and for seating the prosthodontic or orthodontic device in place in the mouth. Both resin based composites and water-based cements can be used as restorative filling materials if properly formulated.
The materials described above are available as multi-part systems, typically in two-parts. These can be in any combination of powder, liquid, or paste. Shelf stability of the individual parts is extremely important so that there is no change in viscosity, color or any other property occurring during the shelf life of the material (typically 2–4 years). In use, the parts are mixed together and then applied. Setting should occur in a short period of time so that the procedure is not uncomfortable for the patient or the operator. The setting characteristics should allow for sufficient time for mixing the materials and applying to the tooth preparation and/or prosthodontic or orthodontic device in place in the mouth.
Certain additives are used in such compositions in order to improve stability; however, some useful additives also alter the setting characteristics unpredictably, provide adverse colorants, alter the viscosity, or generate potential toxic or narcotic by-products. Thus, there is a need for compositions that are more medically acceptable.